1. Field of the Invention
The present invention relates to an electrostatic chuck upwardly sucking and supporting a substrate in a vacuum chamber and an organic light emitting manufacturing apparatus having the same.
2. Description of the Related Art
An organic light emitting diode (hereinafter, referred to as an “OLED”) is a self-luminescent display device emitting light using phenomenon in which electrons and holes, which are injected through an anode and a cathode in an organic thin film of single molecular weight compound, low molecular weight compound, or polymer, are recombined with each other and form excitons and light of a specific wavelength is emitted by energy from the excitons.
An indium tin oxide (ITO) layer having a low surface resistance and excellent permeability can be used as an anode layer of the OLED. In order to increase luminous efficiency, an organic thin film having a multiple structure of hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer (EIL) can be used. A metal layer such as LiF—Al can be used as a cathode layer.
Since an OLED display device using the OLED has excellent characteristics such as a wide viewing angle, a short response time, a low power consumption, and high brightness and is made very light in weight and very thin, the OLED display device is spotlighted as a next generation display. In spite of the excellent characteristics, an apparatus for manufacturing the OLED in commercial quantity is not standardized yet and therefore there is an urgent demand for development of an adequate manufacturing apparatus.
The manufacturing process of the OLED has a pre-process, a post-process, and an encapsulating process. The pre-process is a process of forming the ITO layer on a glass substrate mainly using a sputtering technology, and the manufacturing process for an LCD display is already commercialized. The encapsulation process is a process of encapsulating the organic thin film in order to increase life time of the OLED because the organic thin film is very weak against to moisture and oxygen in air. The post-process is a process of forming the organic thin film and a metal thin film on the glass substrate. As the post-process, a vacuum deposition of forming pixel patterning using a shadow mask on the glass substrate by evaporating the organic material under high vacuum atmosphere is mainly utilized.
It is important how to maintain the high vacuum during the post-process and how to achieve the high rate deposition as necessary requirements for the mass production of the OLED, and a large area substrate greater than 370×470 mm can be used in detail. Particularly, deflection of the large area substrate and the metal mask due to thermal expansion can be restricted at their maximum. These requirements are necessary even to guarantee uniformity of the organic thin film under ±5% in a face-down deposition of putting material to be deposited in a crucible to heat and evaporate the same and thus of forming a thin film on a substrate positioned above the crucible.
An electrostatic chuck can be used as a device for upwardly supporting the substrate in the deposition chamber. The electrostatic chuck is used so that the deflection of the substrate can be minimized.
However, in order to support the large area substrate with a sucking force, high voltage of several kV is applied to the electrostatic chuck. In this case, during the following dechucking, the substrate is not easily separated from the electrostatic chuck due to electrostatic charges remaining on the electrostatic chuck. That is, since, even after the high voltage for the electrostatic chuck is cut off, some of the electrostatic charges remain between the electrostatic chuck and the substrate, the electrostatic chuck still has a sucking force against the substrate. The sucking force makes handling of the substrate be difficult and causes a handling error. Therefore, time for the manufacturing process is increased and manufacturing efficiency is decreased.